EN Welding Standards: EN 1090, EN ISO 15614 and 3834

A fabricator in Rotterdam finished a batch of stair stringers, printed CE on the delivery note and shipped them. Two weeks later the client’s structural engineer asked for the WPQR behind the welds — and the shop could not produce one. Nobody had broken a rule on purpose; the job had simply never passed through the EN welding standards system the contract assumed. That gap is far more common than the paperwork suggests, and understanding it is the difference between a shop that gets invited back and one that gets blacklisted.

What EN Welding Standards Actually Are (and What the ‘EN’ Means)

Search for “EN welding standards” and you will find yourself buried in numbers. There is no single rulebook titled EN Welding Standards. What exists is a large, interlocking family of documents drafted by different technical committees, tied together by a shared numbering system and, more importantly, by a legal framework that decides which parts actually bind your particular job. Getting the vocabulary right is the first step to knowing which document to reach for when a client, an inspector or a notified body asks.

EN: a European Standard, agreed at European level

EN stands for European Standard. Full ENs are developed and published by CEN (the European Committee for Standardization) or CENELEC (the European Committee for Electrotechnical Standardization). Both follow the same three-stage route: a proposal, a formal vote by member countries, and publication. When member countries adopt an EN as their national standard, it becomes binding in each of their territories.

That last point is the one with teeth. EN 1090-2, covering the technical requirements for steel structures, is referenced as a harmonised standard under the EU Construction Products Regulation. That is precisely why it drives CE marking for structural steel: put a steel structure on the EU market and you are working inside a legal framework, not a voluntary code of good practice. The EU’s own guidance on CE marking is blunt about what that means: no central EU body grants permission to use the CE mark. The manufacturer assembles the evidence and, where required, involves a notified body.

EN ISO: adopted at European level, not rewritten

An “EN ISO xxxx” number means the ISO text has been adopted unchanged at European level. The ISO document is the source. CEN adds a European foreword, and occasionally a national foreword, but the clauses, figures and technical requirements are the ISO ones.

This is the single most useful fact for a shop outside Europe. If your colleague says “we weld to ISO 15614-1” and you pull up the national mirror of EN ISO 15614-1, you are reading the same requirements in the same order. The same holds for EN ISO 9606-1 (welder qualification) and the EN ISO 3834 family (quality requirements). ISO keeps the current editions of these documents listed under its welding and joining standards catalogue and the ICS 25.160 welding classification, a practical way to confirm what is current before quoting a clause number.

EN, BS EN, DIN EN, NF EN: same book, different covers

Every EN is republished as a national standard by its member country’s body. The technical content is identical; what differs is the foreword, the national references and, sometimes, minor annotations.

• BS EN — published by BSI in the United Kingdom
• DIN EN — published by DIN in Germany
• NF EN — published by AFNOR in France

If a contract cites “BS EN 1090-2”, it cites the same technical requirements as EN 1090-2. What you must always check is the edition year and any amendments, because a 2005 edition and a current edition are not interchangeable. TWI’s overview of structural steel CE marking and ISO 3834 is a good plain-English explainer on how those pieces fit.

“EN welding standards” is a family, not a document

Here are the entry points most shops actually touch:

Standard	What it governs
EN 1090 (Parts 1 to 4 in widespread use)	Execution of steel and aluminium structures. Part 1 covers general requirements and Factory Production Control, Part 2 the technical requirements for steel structures, Parts 3 and 4 the equivalent for aluminium. Aluminium welding course overviews are worth reading if Part 3 or 4 is in scope for you.
EN ISO 15600 series	Qualification of welding procedures. Part 1 is the workhorse for steel, covering qualification by test and the WPQR that follows. TWI’s guide to welding procedures explains the document chain in plain terms.
EN ISO 3834 series	Quality requirements for fusion welding. Parts 1 to 4 set out how comprehensive the quality regime must be; Part 5 covers personnel certification.
EN ISO 9606 series	Welder qualification testing, steels in Part 1, with separate parts for aluminium, cast iron and copper or nickel alloys. Position and process coverage is where this bites hardest, as an all-position welding rod guide implies. Process-specific routes such as SMAW sit here too, as the case for stick welding shows.
EN 10204	Types of inspection documents, most importantly 3.1 and 3.2 certificates for base material and consumables.

Check the CEN and CENELEC standards catalogue for the live status of each part, because new parts and amendments appear.

Why you cannot simply “follow the EN standard”

There is no universal EN that applies to all welding. Three things select which documents bind you: the product standard (EN 1090 for structural steel, a pressure equipment standard for vessels, a shipbuilding standard for hulls), the execution class or quality level chosen within that product standard, and the contract, which can be stricter than the standard and is what you are legally and commercially bound by. A stair stringer for a private garage and a fatigue-loaded bridge member can both be “EN”, and they will pull completely different parts of the family into scope.

The United Kingdom after Brexit

BS EN standards continue to be used in Great Britain, and CE recognition continues for many construction products, including structural steel. The mechanics still move: conformity assessment routes, designated standards and the UKCA/CE transition have shifted more than once. HSE’s welding guidance remains the reference for UK health and safety duties. Confirm the current requirements before shipping to Great Britain rather than assuming the EU position applies unchanged.

The EN Standards Stack: Which Standard Governs What

Most published lists of EN welding standards read like a shopping list. They are not. The standards sit in a stack, and each layer answers a different question: is the plate fit for the job, is the consumable approved, is the procedure qualified, is the welder qualified, is the work coordinated, and can you prove all of it three years later? Get the order wrong and the paperwork fails even when the steel is perfect.

The map below covers the standards most fabricators, coding shops and inspection houses work with, drawn from the current ISO welding catalogue and the CEN/CENELEC standards catalogue.

Standard	What it actually controls
EN ISO 3834 Parts 1 to 6	Quality framework for fusion welding: Part 1 selection criteria, Part 2 comprehensive, Part 3 standard, Part 4 special, Part 5 personnel certification, Part 6 implementation guidance (2024).
EN ISO 15607:2019	General rules for the specification and qualification of welding procedures.
EN ISO 15609-1:2019	How a WPS is written down: what must be recorded, in what order.
EN ISO 15614-1:2017	Procedure qualification by test: arc and gas welding of steels, arc welding of nickel and nickel alloys.
EN ISO 15614-2:2025	Procedure qualification by test for arc welding of aluminium and its alloys.
EN ISO 15610:2024 / 15612:2018 / 15613:2025	Alternative qualification routes: tested consumables, adoption of a standard welding procedure, pre-production welding test.
EN ISO 9606-1	Welder qualification testing for steels, plus sibling parts for aluminium, cast iron and copper/nickel alloys.
EN ISO 14732	Qualification and certification of welding coordination personnel.
EN 1090-2	Execution of steel structures: technical requirements and the EXC1 to EXC4 classes.
EN ISO 5817:2023	Acceptable imperfections in welded joints: quality levels B, C and D.
EN ISO 13920:2023	General tolerances for welded constructions (dimensional).
EN ISO 9013 + 2024 amendment	Tolerances for thermally cut edges.
EN ISO 9692-2:2024 and -3:2016	Joint preparation: submerged arc welding, and aluminium.
EN 10204	Types of inspection documents, most importantly type 3.1 and type 3.2.
EN ISO 17637 / 17638 / 17639 / 17640	Non-destructive testing: visual, ultrasonic, radiographic and magnetic particle.
EN ISO 9712	Qualification and certification of NDT personnel.
EN ISO 17663	Quality assurance in NDT, after and during production.
EN 1093 and EN 12492	Protective equipment: fume extraction and head protection.

How the layers connect

The stack is a chain of evidence and it only runs one way, from raw material to finished weld. TWI’s procedure guidance explains why: the WPQR and the welder certificate only mean something because a documented chain supports them.

1. Material certification. Mill certificates in EN 10204 format, traceable to heat and batch. You cannot qualify a procedure on plate of unknown origin.
2. Consumable certification. Approved filler and consumables, batch traceability tying the wire in the gun to the certificate in the file.
3. Procedure qualification. A qualified pWPS, a test coupon and a WPQR setting the ranges you may work within. The ISO welding standards index lists the alternative routes.
4. Welder qualification. EN ISO 9606 certificates matching the process, position, thickness range and diameter of the work in front of you.
5. Coordinated execution. A named welding coordinator under EN ISO 14732, working inside the EN 1090 execution class the contract demands.
6. Inspection and documentation. NDT by qualified personnel under EN ISO 9712, acceptance judged against EN ISO 5817 at the specified level, dimensions to EN ISO 13920 and EN ISO 9013, all in the technical file.

Why a perfect weld can still fail

A weld can be metallurgically beautiful and still be non-compliant. An undercut a level D job would wave through can be a rejection at level B. A sound weld from a welder certified for 3 mm to 10 mm is not qualified work on 20 mm plate. A fillet run outside the WPQR heat input window is outside the procedure, whatever it looks like. Compliance under EN 1090 and the ISO 3834 family is as much documentary as technical, and inspectors weigh both halves equally.

That is why ISO 15614-1 matters so much. It covers arc and gas welding of steels and arc welding of nickel and nickel alloys using the ISO 4063 process numbers, and it defines what a qualified range actually means. Its recent siblings ISO 15614-2:2025 and ISO 15613:2025 sit alongside it in the current catalogue.

Read the stack again and the shape of the job is clear. ISO 3834 supplies the management framework, ISO 15614 and ISO 9606 the technical evidence, EN 1090 the execution classes and the route to CE marking, and EN ISO 5817 and EN ISO 13920 the acceptance criteria. All of it is documented in the quality management side of CE marking, and all of it must hold together when someone asks for the file three years later.

EN ISO 15614: Qualifying Welding Procedures and WPQRs

A qualified welding procedure is not a document you write at a desk. It is the record of a test that somebody welded, examined and signed. That distinction is the whole point of EN ISO 15614-1, and it explains how a shop full of competent welders can still fail an audit over paperwork. The chain is short: a preliminary WPS, a test piece welded to it, the qualification record, then a production WPS derived from that record.

The document chain, step by step

Stage	Document	What it actually is
1	pWPS (preliminary WPS)	A draft instruction: joint design, material group and thickness, process, consumable, positions, parameters, heat input range and sequence. A working document, not evidence.
2	Test piece	Welded by a qualified welder, normally to the pWPS, in the shop. Geometry, length and quantity are set by the standard.
3	Examination	Visual, macro-examination, transverse bend, fillet break and impact testing where the joint type and service conditions call for it.
4	WPQR (qualification record)	Results, tested parameters and the resulting ranges of qualification. This is the evidence document.
5	Production WPS	Derived from the WPQR and written for the welder. It may not exceed any qualified range.

Step four is where shops get it wrong. A WPQR is a historical record of a specific test, not a work instruction, and nobody should ever weld to a WPQR. You weld to a production WPS, and that production WPS is only defensible because a WPQR sits behind it. TWI’s guidance on procedure qualification spells out the same logic: the test exists to demonstrate that the stated ranges produce sound welds.

Level 1 and level 2: the logic runs backwards from expectation

Two test levels exist, and the relationship between them surprises people. A level 1 test is the lighter test, yet it qualifies a wider range of production work. A level 2 test involves more extensive testing and more demanding examination, and the range it qualifies is narrower and more tightly defined.

Because level 2 is the harder test, a level 2 qualification automatically satisfies level 1 requirements. The reverse is not true. A level 1 qualification can never be presented as level 2.

Level 1 still appears in practice, usually on less demanding work or on qualifications predating current rules. For new structural steel work under EN 1090-2, level 2 is the safe assumption, but read the clause rather than assume it.

Test pieces, examinations and what the results qualify

Three test piece geometries cover most production: butt, fillet and T-joint. A butt test is normally sectioned for macro-examination and bent transversely, face and root, to prove ductility and sound fusion. A fillet test is broken open to reveal the root, showing whether penetration reached it without cutting the whole section. T-joint tests cover combinations the others cannot, and impact testing is added where toughness matters, such as low service temperatures or fatigue-loaded structures.

Pass the tests and you still have not finished. The results define the qualifying ranges, and every production weld must sit inside them:

• Joint type (butt, fillet, partial penetration, T-joint)
• Material thickness range
• Pipe diameter range, where relevant
• Welding positions
• Material group, using the standard’s group numbers
• Welding process, for example 135, 141 or 111

That list is why a WPS range that does not cover production is such a common audit finding. A shop that qualified in flat and horizontal fillet and then welds vertical pipe has left the qualified range, regardless of how good the weld looks. For process context, why SMAW still wins is worth reading, because SMAW is frequently the qualifying process for structural fillet work even when the production order itself is MAG or TIG.

Alternative routes to a qualified procedure

• EN ISO 15610 qualifies a procedure on the basis of tested consumables. If you use consumables approved and certified under the EN ISO 14171 and EN ISO 14172 series and follow the manufacturer’s tested data, you can qualify with fewer joints. It is the fast route for MAG and TIG work with approved consumables, including much aluminium MIG production.
• EN ISO 15612 covers adoption of a standard welding procedure. You adopt a published standard procedure and demonstrate compliance through a limited test. The qualification stays inside that standard procedure, which is why shops use it for standardised joints and avoid re-testing near-identical details.
• EN ISO 15613:2025 covers the pre-production welding test. A production-type test piece is made and tested in the shop as a bridge between qualification and routine production, useful where product-specific conditions or consumable data carry the qualification.

Consumables, certificates and traceability

Every consumable inside a qualified procedure must be approved and traceable. That means an EN 10204 inspection document: type 3.1 issued under the manufacturer’s own quality system, or type 3.2 independently certified by a third party. EN ISO 14171 and EN ISO 14172 set the technical delivery conditions and manufacturer requirements behind those certificates. Batch or lot numbers must be recorded so any weld traces back to the consumable that made it. The ISO consumables category confirms which approval standard applies to the product you are buying.

Keeping the qualification current

ISO 15614-1:2017 was last reviewed and confirmed in 2022 and carries Amendment 1:2019, and the ISO catalogue now shows an ISO/DIS 15614-1 under development, so a revision is approaching. Clause references change. Part 11:2025 covers electron and laser beam welding. Procedures qualified against previous editions may still be used, and in defined cases a new WPQR range can be built from an existing WPQR where additional testing preserves technical equivalence. Check ISO’s welding standards listings before quoting clause numbers in a specification or an audit response.

EN ISO 9606 and EN ISO 14732: Qualifying Welders and the People Around Them

A qualified procedure says how to make the joint. A separate system says whether a particular person can make it properly, day after day: EN ISO 9606 for welder qualification, paired with EN ISO 14732 for the people who police the procedures.

What EN ISO 9606-1 Actually Covers

The series has one part per material family. Part 1 covers fusion welding of steels and is the part most structural shops need; the siblings cover aluminium, cast iron, and copper and nickel alloys. A steels certificate does not extend to aluminium TIG work.

Part 1 appears in the ISO welding standards catalogue alongside the procedure qualification standards, and the test breaks down logically:

1. The candidate welds a test piece using an already qualified procedure, a WPS backed by a WPQR.
2. The test piece is visually examined, then macro-examined by cutting it open to check fusion and penetration.
3. It is then bend tested or fracture tested: no significant cracking in the bend, sound fusion across the section in the fracture.

Pass, and you get a certificate carrying a qualification range: process, position, material group, thickness range and, for tube work, diameter range. That range defines where the welder may work. Positions catch shops out. Flat and horizontal is not vertical or overhead, and 5 mm plate is not 20 mm.

What a Certificate Does and Does Not Prove

A current certificate proves that one specific person, on a specific date, passed a specific test using a specific qualified procedure. It says nothing about that welder’s work six months later, and it does not replace procedure qualification.

The two systems are independent. A WPS does not make a welder qualified. A welder cannot be sent outside the range on their certificate, however experienced they are. A vertical 12 mm butt weld in 355 plate against a certificate covering flat 6 mm mild steel is a nonconformity with a name and a number on it.

What the test confirms is sound, consistently fused metal to a written procedure, with defects limited to those the procedure allows and the inspector can accept. That is why the test piece is always welded to a qualified procedure.

Keeping Qualifications Current

EN ISO 9606-1 sets out how to qualify a welder. It lays down no universal expiry date, and no clause says a certificate dies at twelve months. That duty sits elsewhere: EN 1090 and the contract specification require qualified personnel and demonstrated continued competence. TWI’s guidance on structural steel CE marking sets out the ISO 3834 framework EN 1090 work sits inside, where personnel competence is one pillar.

In practice, the convention is that a welder who has not welded in a given process for roughly six to twelve months re-tests before returning to it. Flag that as shop practice and contract language, not as a clause quoted from ISO 9606-1. Write your own re-qualification rule into the system.

Continuity records prove the shop took this seriously: a dated log of what each welder welded, on what material, to what process and thickness, with certificates on file. Without it, you are asking the auditor to take your word for it.

EN ISO 14732: The People Who Hold the System Together

EN ISO 14732 covers qualification and certification of welding coordination personnel, across three roles that are not interchangeable:

• Welding coordinator — the organiser and planner: schedules work, assigns qualified welders and procedures to joints, liaises with the client and inspection bodies, keeps the documentation trail alive.
• Welding engineer — the technical authority who develops and qualifies procedures, resolves technical queries and assesses deviations.
• Welding technical specialist — a support role for the detailed technical and organisational tasks between the two.

It is not a standalone rulebook. It works alongside EN ISO 3834-5, which deals with personnel certification inside the ISO 3834 quality system. Part 1 of that family gives criteria for selecting the level of quality requirements; Part 2, the comprehensive requirements, was reviewed by ISO in 2026, so check for amendments before quoting clauses.

Many EN 1090 contracts require a named, qualified welding coordinator with documented authority, named in the technical file with the certificate attached rather than left informal for whoever is senior on the day. Authority matters most: the coordinator needs documented power to stop work when a weld falls outside a qualified procedure, a consumable has no traceable certificate, or a welder’s range does not cover the joint. A coordinator without that authority is a signature, not a control.

Connecting Personnel to the Wider Framework

Personnel qualification is one strand. The TWI overview of welding procedure qualification covers the procedural side, the ISO 3834 series the management system tying procedures, welders, consumables, inspection and records together, and the EN standards on CE marking the third-party oversight layer for structural products on the EU market.

Keep personnel certification as current as welder certification: if a coordinator’s certificate lapses or the role changes, the technical file has a hole in it. Keep welder certification aligned with the material families you actually weld. A shop moving into aluminium needs the aluminium qualification route, not a steels certificate by assumption. Guides to aluminium MIG welding and aluminium welding courses cover technique, but the paper qualification is a separate requirement from the training.

Handled properly, personnel qualification turns a set of standards into something a client can rely on: the procedure says what good looks like, the welder certificate says who can deliver it, the coordinator certificate says someone with the authority is watching. Miss one and the chain breaks.

EN 1090: Execution Classes EXC1 to EXC4 and What Actually Changes

EN 1090 turns a welding shop into a supplier of construction products. It is not a procedure standard and never tells you how to run a bead. It tells you what kind of company you must be, what records you must keep, and what an inspector is entitled to demand when they open a file. For any shop selling structural steel into the EU market it is binding rather than optional, because EN 1090-2 is a harmonised standard under the Construction Products Regulation. That is why the CE mark on a delivery note is not a marketing flourish but a legal claim about the entire production system behind the steel.

The four parts, and why the part number matters

• EN 1090-1 sets out the general requirements: the Factory Production Control (FPC) manual, notified body involvement, the Declaration of Performance (DoP) and the CE marking itself.
• EN 1090-2 holds the technical requirements for steel structures. Execution classes, welding, tolerances, bolting, cutting and testing all live here.
• EN 1090-3 and EN 1090-4 do the equivalent job for aluminium, one covering general requirements and one the technical side for aluminium structural elements. Aluminium work has its own traps, and filler metal and shielding gas choices differ enough from steel to be worth reading up on, as in this practical guide to aluminium MIG welding.

Confirm the current part list in the CEN/CENELEC standards catalogue before quoting clause numbers, because the series is revised and amended.

The four execution classes

Execution class is the mechanism EN 1090 uses to match the level of assurance to the risk of the structure. TWI’s guidance on structural steel CE marking and ISO 3834 notes that BS EN 1090 Part 2 divides construction products into four execution classes, with EXC1 covering unwelded items and welded items not subject to dynamic loading.

Class	Typical scope	Worked example
EXC1	Simple, statically loaded elements; often not welded at all	Straight columns, base plates, simple stair stringers in a non-critical building
EXC2	Ordinary building and static structures	Primary beams, bracing, typical structural steel for a commercial building
EXC3	Structures subject to dynamic or fatigue loading	Bridge girders, crane runway beams, structures with significant cyclic loading
EXC4	Highly loaded or fatigue-critical structures	Major bridge components, fatigue-sensitive details, high consequence structures

What actually changes as you move up the classes

• Quality management system. EN 1090-2 requires welding on covered structures to be carried out under a quality system meeting the ISO 3834 series, typically EN ISO 3834-2 for comprehensive requirements. The higher classes demand more documented control, not just more welder hours.
• Qualified procedures. At EXC1 a full production WPS set may not be demanded. From EXC2 upward, work is expected to run to qualified procedures, with each production WPS traceable to a WPQR that actually covers the joint type, thickness, position, material group and process used in production.
• Imperfection acceptance. EN ISO 5817:2023 is the reference for acceptable defects, and the commonly applied mapping is EXC1 to quality level D, EXC2 to C, and EXC3 and EXC4 to B. Level D tolerates considerably more than B, so a defect that passes on a simple job can be a rejection on a bridge.
• Dimensional tolerances. EN ISO 13920:2023 (general tolerances for welded constructions) sets the framework, with EN 1090-2 applying tighter tolerance regimes as the class rises. Profile, section and fabrication geometry all tighten together, which affects cutting, fit-up and the amount of grinding a shop can absorb.
• Non-destructive testing. Coverage expands step by step, and the ISO welding standards family sets the method and personnel rules for the NDT itself.

The NDT coverage most shops quote runs along these lines: EXC1 relies on visual inspection alone; EXC2 adds magnetic particle testing to a sample of fillet welds; EXC3 introduces ultrasonic or radiographic testing of a proportion of butt welds alongside fillet sampling; EXC4 approaches near-total butt weld NDT with a higher fillet sample. Treat that as a working summary only. The percentages, sampling rules and exceptions sit in the normative tables of EN 1090-2, and they differ for butt welds, fillet welds and specific joints. Check the table before promising a coverage figure to a client.

The certification chain behind the CE mark

Everything above is evidenced through a chain, and an auditor usually follows it in order:

1. FPC manual describing how the factory controls specification, materials, consumables, equipment, welding, inspection and non-conformity.
2. Named welding coordinator, qualified to EN ISO 14732, with the authority to hold or stop work.
3. Internal audits and production samples, showing the system is live rather than a document written once.
4. The technical file, holding material certificates, consumable certification, WPQRs, welder certificates, weld maps, NDT reports and inspection records.
5. The Declaration of Performance and Declaration of Conformity, with the CE marking and the notified body identification number where a third party was involved.

EU guidance on CE marking is explicit that the declaration of conformity and the supporting technical documentation must be retained for at least ten years after the product is placed on the market. For a small shop that is rarely the problem. The problem is a file that cannot be produced on request because the welder certificates were never scanned in and the WPS lived on a whiteboard.

EN ISO 3834 and EN ISO 5817: Quality Management and Acceptable Defects

Two standards do the heavy lifting underneath EN 1090, and they do very different jobs. EN ISO 3834 is the management framework: how a welding organisation runs itself. EN ISO 5817 is the acceptance sheet: whether a finished weld is good enough. EN 1090 borrows its execution classes from the first and its defect criteria from the second, which is how a shop can follow every documented process and still fail a job when the welds fall outside the specified quality level.

It helps to place them in the wider family. ISO 15614 and ISO 9606 produce the technical evidence. ISO 3834 keeps that evidence alive, traceable and current. ISO 5817 delivers the verdict on the finished joint.

The ISO 3834 family, part by part

The family was restructured and its parts 1 to 5 were all revised in 2021. Part 1 is the selection criteria, a short document that helps an organisation decide which other part applies. Part 2 sets comprehensive quality requirements, and this is the one most EN 1090 work is written against. Part 3 is the standard level, for organisations whose welding is governed by other recognised technical specifications and where a full documented system is not proportionate. Part 4 covers special applications, including specific material or process requirements such as aluminium. Part 5 deals with certification of welding coordination personnel, and Part 6, published in 2024, gives practical guidance on implementing the family.

The scope of each part can be reviewed in the ISO welding standards catalogue, and the standard level described in ISO 3834-3 is a useful contrast to the comprehensive requirements of Part 2.

How an organisation chooses its level

Nobody picks a 3834 level in the abstract. The contract decides. EN 1090-2 calls for comprehensive quality requirements to ISO 3834-2 for the higher execution classes, and a fabricator who cannot show a functioning quality system simply cannot take that work, however good the welds look. Where the work is simpler or the contract permits it, Part 3 may be defensible; Part 4 is for special applications outside the ordinary steel envelope.

Because Part 1 exists for exactly this reason, choosing wrongly is a common audit finding. A shop that implemented Part 3 while the contract demanded Part 2 has not just made a paperwork error; it has been operating without controls the contract assumed were in place.

What a comprehensive quality system looks like day to day

In practice, a Part 2 system is a documented set of habits rather than a large manual nobody opens. The core elements are recognisable from any successfully audited shop:

• Base material control with heat numbers, EN 10204 certificates and segregation at goods-in.
• Consumable control, including batch traceability for electrodes, wire and gas. Choosing the right filler is only half of it; see this all-position welding rod guide for the electrode side, and the consumables branch of the ISO welding catalogue for approval standards.
• Qualified procedures and welders, so production welding always follows a procedure that has actually been tested.
• Equipment verification: current calibration for measurement and test equipment, documented maintenance for power sources and wire feeders.
• Environmental control, including preheat, interpass and heat maintenance temperatures measured and recorded. ISO 13916:2025 is the current guidance on that measurement.
• Inspection and test planning, non-conformity handling, weld maps, quality records and a schedule of internal audits.

Cutting fits in here too. ISO 9013:2017 with Amendment 1:2024 governs the classification of thermal cuts and their geometrical tolerances, and it applies to every profile that later feeds a welded assembly.

The link between this system and CE marking is well explained in TWI’s overview of structural steel CE marking and ISO 3834. High-integrity fabricators, aerospace shops in particular, live with the same logic at a more demanding scale, as described in the aerospace welding standards and careers guide.

EN ISO 5817:2023 and the three quality levels

ISO 5817:2023 sets quality levels for imperfections in fusion-welded joints in steel, nickel, titanium and their alloys. Beam welding is excluded from its scope, and aluminium is not covered either, so aluminium work runs under EN 1090-4 with its own acceptance references.

Level	What it means	Typical EN 1090 mapping
B	Highest level, tightest limits on imperfection size and type	EXC3 and EXC4
C	Intermediate level for ordinary structural work	EXC2
D	Lowest level, used where the design can tolerate larger defects	EXC1

The imperfection types it addresses include cracks, lack of fusion, incomplete penetration, excess weld metal, undercut, overlap, porosity and solid inclusions. The levels are catalogued in the ISO welding quality standards category.

Here is the point that trips up experienced inspectors: acceptance is not a matter of opinion, craft judgement or how good the weld looks. A discontinuity is acceptable or it is not, measured against the limits set for the specified level. If the contract says level C, a defect that would pass at B still fails; if it says B, a defect a tired inspector would wave through at D is a rejection.

EN Welding Standards vs AWS and ASME: Why the Difference Matters on Export Work

Consider a shop in Ohio that has welded bridge girders for twenty years under AWS D1.1. A European client now asks for EN 1090-2 EXC3, an ISO 15614 WPQR, an ISO 14732 certified coordinator and a Declaration of Performance. The welds are identical; the paperwork is not, and the shop must rebuild its quality system. Both frameworks answer “is this weld good?” differently, and that gap stops fabricators from quoting work they cannot document.

Two philosophies, not two dialects

The EN framework is management-system based. EN 1090 assumes a quality system built on EN ISO 3834, a Factory Production Control (FPC) manual, internal audits, qualified coordination personnel and third-party assessment by a notified body. Conformity is designed into the product standard itself, which is why CE marking for structural steel in the EU cannot exist without it.

AWS and ASME codes are prescriptive. AWS D1.1 and ASME Sections I, II and IX tell you what the joint must look like, how the procedure must be qualified and what the welder must demonstrate, with conformity proven by qualified procedures, qualified welders and inspection agency oversight. The American Welding Society has authored more than 350 standards for welding practices and procedures, and the ASME portfolio covers pressure technology, power plants and piping, with Section IX handling welder and operator qualification.